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United States Patent |
5,231,838
|
Cieslukowski
|
*
August 3, 1993
|
No loss single line fueling station for liquid natural gas vehicles
Abstract
A vacuum insulated storage vessel holds a quantity of LNG for delivery to a
pressure building tank. The pressure building tank maintains a natural gas
head over the LNG. The pressure in the pressure building tank is lowered
using liquid nitrogen (LN.sub.2) to condense the natural gas head and is
raised by vaporizing the LNG. A valve system connects the supply of LNG in
the pressure building tank to the fuel tank of the vehicle being supplied
to allow either LNG or natural gas to be delivered to the vehicle tank and
allows natural gas in the tank to be vented back to the fueling station.
The fueling station of the invention includes suitable controls for
controlling the pressure and temperature of the LNG delivered to the
vehicle, the pressure and temperature in the fueling station itself and
the pressure and temperature in the vehicle fuel tank.
Inventors:
|
Cieslukowski; Robert E. (New Prague, MN)
|
Assignee:
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Minnesota Valley Engineering, Inc. (New Prague, MN)
|
[*] Notice: |
The portion of the term of this patent subsequent to June 16, 2009
has been disclaimed. |
Appl. No.:
|
837168 |
Filed:
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February 18, 1992 |
Current U.S. Class: |
62/50.4; 123/525; 123/527 |
Intern'l Class: |
F17C 009/04 |
Field of Search: |
62/50.4
123/525,527
|
References Cited
U.S. Patent Documents
3183678 | May., 1965 | Hosford | 62/50.
|
3898853 | Aug., 1975 | Iung | 62/50.
|
4018582 | Apr., 1977 | Hinds et al. | 62/50.
|
4080800 | Mar., 1978 | Spaulding et al. | 62/50.
|
Primary Examiner: Capossela; Ronald C.
Attorney, Agent or Firm: Rockey, Rifkin and Ryther
Parent Case Text
This application is a continuation-in-part of application Ser. No.
07/702,075, now U.S. Pat. No. 5,121,609.
Claims
What is claimed is:
1. A no loss fueling station for delivery of liquid natural gas (LNG) to a
fuel tank of a use device such as a motor vehicle, comprising:
a) a pressure building tank holding a quantity of LNG and a natural gas
head;
b) first means for selectively building the pressure and temperature in the
pressure building tank;
c) second means for selectively reducing the pressure and temperature in
the pressure building tank;
d) means for controlling the first and second means to maintain a desired
pressure and temperature in the pressure building tank without venting
natural gas to the atmosphere; and
e) means for delivering LNG from the pressure building tank to the use
device.
2. The fueling station according to claim 1, wherein the first means
includes means for vaporizing LNG in the pressure building tank thereby to
increase the pressure therein.
3. The fueling station according to claim 1, wherein the second means
includes means for condensing the natural gas head in the pressure
building tank.
4. The fueling station according to claim 1, wherein said means for
condensing includes a heat sink disposed in the gas head portion of said
pressure building tank and means for passing relatively cooler fluid
through said heat sink thereby to condense the gas head and reduce
pressure.
5. The fueling station according to claim 1, further including means for
selectively sub-cooling the LNG before delivering it to the use device.
6. The fueling station according to claim 5, wherein the means for
selectively sub-cooling includes a heat exchanger having relatively cooler
fluid passing therethrough.
7. The fueling station according to claim 1, further including means for
filling said pressure building tank with LNG.
8. The fueling station according to claim 1, wherein the means for
delivering further includes means for delivering natural gas to the use
device fuel tank and for first delivering natural gas from the use device
fuel tank to the fueling station if necessary to create a pressure
differential to permit refilling.
9. The fueling station according to claim 8, wherein said delivering means
includes an injector means having a single output port, a plurality of
input ports and means for connecting the output port with one of the input
ports.
10. The fueling station according to claim 9, further including a first
means for communicating the LNG in said pressure building tank to said
injector means.
11. The fueling station according to claim 9, further including a second
means for communicating the gas head in said pressure building tank to
said injector means.
12. A no loss fueling station for delivery of liquid natural gas (LNG) to a
fuel tank of a use device such as a motor vehicle, comprising:
a) a pressure building tank holding a quantity of LNG and a natural gas
head;
b) means for delivering LNG to the pressure building tank;
c) means for selectively raising the pressure and temperature in the
pressure building tank;
d) means for selectively reducing the pressure and temperature in the
pressure building tank;
e) means for controlling the means for selectively raising and the means
for selectively reducing to maintain a desired pressure and temperature in
the pressure building tank without venting natural gas to the atmosphere;
and
f) means for delivering either LNG or natural gas from said pressure
building tank to the fuel tank of the use device such that both the
temperature and pressure in the fuel tank can be controlled.
13. The fueling station according to claim 12, wherein said delivering
means includes a storage tank holding a quantity of LNG greater than that
in said pressure building tank and a gas head.
14. The fueling station according to claim 13, further including means for
communicating the gas head in the pressure building tank with the gas head
in said storage tank.
15. The fueling station according to claim 12, wherein the means for
raising means includes means for vaporizing LNG in the pressure building
tank thereby to increase the pressure therein.
16. The fueling station according to claim 12, wherein the means for
reducing pressure includes means for condensing the natural gas head in
the pressure building tank.
17. The fueling station according to claim 16 wherein said means for
condensing includes a heat sink disposed in the gas head portion of said
pressure building tank and means for passing relatively cooler fluid
through said heat sink thereby to condense the gas head and reduce
pressure.
18. The fueling station according to claim 12, further including means for
selectively sub-cooling the LNG before delivering it to the use device.
19. The fueling station according to claim 12, wherein said means for
delivering includes means for delivering natural gas from the use device
to the fueling station to create a pressure differential to permit
refilling.
20. The fueling station according to claim 19, wherein said means for
delivering further includes an injector means having a single output port,
a plurality of input ports and means for connecting the output port with
one of the input ports.
21. The fueling station according to claim 20, further including a first
mean for communicating the LNG in said pressure building tank to said
injector means.
22. The fueling station according to claim 20, further including a second
means for communicating the gas head in said pressure building tank to
said injector means.
Description
BACKGROUND OF THE INVENTION This invention relates, generally, to liquid
natural gas (LNG) delivery systems and, more specifically, to a no loss
fueling station for LNG particularly suited for use with natural gas
powered motor vehicles.
America's dependence on foreign sources of fuel oil has resulted in
significant political and economic problems in recent years. As a result,
great efforts have been made to find a cheaper and more reliable domestic
energy alternative. One such alternative is natural gas which is
domestically available, plentiful, relatively inexpensive and
environmentally safe as compared to oil. Because one of the largest uses
for oil is as a fuel for motor vehicles, great strides have been made to
develop alternative fuels including natural gas.
One possibility is a dual-fuel modified diesel engine which runs on a 60/40
diesel fuel to LNG mixture. While this engine substantially reduces diesel
fuel consumption, it requires that LNG be delivered to the engine at
approximately 300 psi, a pressure approximately 6 times the normal storage
pressure for LNG. Other natural gas powered engines require that the LNG
be delivered at pressures ranging from less than 50 psi to more than 500
psi. Therefore, a LNG fueling station that can deliver LNG to vehicles
having wide variations in delivery pressure requirements is desired.
Moreover, fueling must be accomplished such that when the filling
operation is completed the pressure of the vehicle's filled tank is at
least as high as the minimum operating pressure of the vehicle, but less
than the venting pressure of the tank.
Moreover, LNG is an extremely volatile substance that is greatly affected
by changes in pressure and temperature. As a result, the fueling station
must be able to accommodate fluctuations in pressure and temperature and
transitions between the liquid and gas states resulting from heat
inclusion that invariably occurs in cryogenic systems. Optimally, the
fueling station should be able to meet these conditions without venting
LNG to the atmosphere because the venting of LNG is wasteful and
potentially dangerous.
Thus a no loss LNG fueling station that is efficient, safe and can deliver
LNG at a range of temperatures, pressures and operating conditions is
desired.
SUMMARY OF THE INVENTION
The fueling station of the invention consists of a vacuum insulated storage
vessel for storing and delivering LNG to a pressure building tank. The
pressure building tank holds a quantity of LNG with a natural gas head.
The pressure in the pressure building tank is lowered by condensing the
natural gas using a liquid nitrogen (LN.sub.2) cooling system and is
raised by vaporizing the LNG through a heat exchanger. A valve system
connects the supply of LNG in the pressure building tank to a single fill
line engageable with the vehicle being supplied to allow either LNG or
natural gas to be delivered to the vehicle tank and to allow natural gas
in the vehicle tank to be vented back to the fueling station. The fueling
station of the invention includes suitable means for controlling the
temperature and pressure of the LNG delivered to the vehicle, the pressure
in the fueling station itself and the pressure in the vehicle's fuel tank.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic view of the fueling station of the invention.
FIGS. 2, 3A and 3B shows details of the two-way injection valve of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring more particularly to FIG. 1, the fueling station of the invention
consists of a storage vessel 1 holding a supply of LNG 2. Storage vessel 1
is a double-walled tank having a vacuum insulated space 3 therein.
Although vessel 1 is insulated, some heat transfer will occur between the
LNG 2 and the ambient environment. At a result, a natural gas pressure
head 5 is created which pressurizes the LNG in vessel 1.
A fill line 7 permits periodic refilling of tank 1 from a LNG transport
such as a truck or railroad car. Fill line 7 splits into a top fill line
7a and bottom fill line 7b. The top fill line 7a sprays a relatively small
portion of the delivered LNG into the gas head 5 such that the gas head 5
condenses. As the gas condenses the pressure in vessel 1 decreases such
that the main portion of LNG being delivered through bottom fill line 7b
is facilitated. The LNG is preferably supplied to vessel 1 from the mobile
supply at approximately 5-10 psi.
An insulated pressure building tank 9 is provided to pressurize the LNG to
the desired pressure for delivery to vehicles such as buses, trucks, vans
and other vehicles typically found in a fleet. A LNG delivery line 11
delivers LNG from the storage vessel 1 to the pressure building tank 9.
Flow of LNG between tank 1 and tank 9 is controlled by valve 12. Delivery
of LNG from vessel 1 to tank 9 can only occur if the pressure in tank 9 is
less than the pressure in vessel 1. Thus, the pressure in tank 9 is
reduced, if necessary, as described hereafter, to a pressure below that in
vessel 1. Typically, the filling operation will occur at a time when no
demand is being made on the system for delivery of LNG.
After tank 9 has been filled with LNG 13 a gas head 15 will be created. A
plastic float 17 is provided between the LNG 13 and gas head 15. Float 17
separates the LNG 13 from the relatively warm gas head 15 to minimize the
heat transfer therebetween and prevent the uncontrolled vaporization
and/or condensation that would otherwise occur. Minimizing this heat
transfer allows the system pressures and temperatures to be more precisely
controlled.
A pressure building line 23 is provided on tank 9 connecting the LNG 13
with the gas head 15. Pressure building line 23 is provided with an
uninsulated coil 25 that maximizes the heat transfer between the LNG in
line 23 and the ambient environment. As a result, the LNG is vaporized in
coil 25 and is delivered to the head 15 as a gas thereby to increase the
pressure in tank 9 when necessary. A pressure sensor 27 is provided in
pressure building line 23 to control valve 29 such that when the pressure
of head 15 falls below a predetermined value, sensor 27 will open valve 29
to allow gas to flow through line 23 and rebuild the head pressure.
A pressure relief line 31 is provided between gas head 5 of vessel 1 and
gas head 15 of tank 9. A pressure regulator 33 is provided in line 31 that
allows gas to travel from head 5 to head 15 when the pressure of head 5
rises above the predetermined value set by regulator 33. Because the
pressure in tank 9 can be controlled, as will hereinafter be described,
the gas pressure from head 5 can be controlled as desired to insure
trouble free delivery of LNG.
A main use line 41 is provided to deliver LNG from tank 9 to a vehicle via
two-way injection valve 45. A low quantity use line 39 connects the LNG in
tank 9 to the main us line 41 at three-way valve 43. Three-way valve 41
is, preferably, electronically operated and can connect the two-way
injection valve 45 with either main use line 41 or low quantity use line
39. A scale 55 is provided on tank 9 to act as a meter to thereby regulate
the amount of LNG delivered to the vehicle.
Main use line 41 is used whenever large quantities, i.e., 10 or more
gallons, of LNG are to be delivered. Main use line 41 delivers the LNG
directly from tank 9 to two-way injection valve 45 via valve 43.
Low quantity use line 39 is used to deliver small quantities, i.e., less
than 10 gallons, of LNG to the vehicle or to lower the temperature in the
vehicle fuel tank. When small quantities of LNG are delivered, heat
transfer to the LNG during its conveyance through the use line becomes
problematic because some of the LNG will vaporize before reaching the
vehicle. For small quantities of LNG, therefore, a heat exchanger 47 is
provided to sub-cool the LNG. Thus, even though small quantities of LNG
are delivered through line 39 the heat transfer to the LNG in line 39 does
not present a vaporization problem because the LNG delivered therethrough
is sub-cooled by liquid Nitrogen (LN.sub.2) as will be described
hereinafter. Sub-cooled LNG can also be delivered through line 39 to cool
the vehicle's LNG system when necessary.
A vent line 49 connects head 15 of tank 9 with two-way injection valve 45.
Specifically, vent line 51 connects head 5 of tank 1 with line 49 at
three-way valve 53. Vent line 51 can be selectively connected to two-way
injection valve 45 by three-way valve 53 to vent high pressure gas from
the vehicle's fuel tank back to head 5. Alternatively, line 49 can be
selectively connected to injection valve 45 by valve 53 to vent high
pressure gas from the vehicle's fuel tank to head 15, if so desired.
Venting the high pressure gas from the vehicle facilitates the delivery of
LNG by lowering the pressure in the vehicle's fuel tank. Alternatively,
if, after the filling operation, the pressure in the vehicle's fuel tank
is too low, vent line 49 can be connected to two-way injection valve 45 to
pressurize the vehicle's tank with high pressure gas from head 15 or to
increase the temperature in the vehicle's LNG system.
A cooling tank 16 holds a supply of liquid nitrogen (LN.sub.2) 20 having a
gas head 18 formed therein as previously described with respect to head 5.
While LN.sub.2 is preferred any suitable condensing agent, such as liquid
oxygen (LOX), may be used. Moreover, a mechanical refrigerator could also
be used. The LN.sub.2 is used as a heat transfer medium to control the
pressure and temperature of the LNG in the system. In this regard, a first
cooling line 57 is provided that passes through head 15 in tank 9. Cooling
line 57 includes vaporizer coil 59 located in head 15 that acts as a heat
sink and maximizes the transfer of heat from head 15 to the LN.sub.2
traveling through line 57. As the LN.sub.2 passes through coil 59, heat is
transferred to the LN.sub.2 such that the head gas 15 is cooled and
condenses. The LN.sub.2 becomes warmer and eventually vaporizes. As the
head gas condenses the pressure in tank 9 will decrease. Thus by
controlling the flow of LN.sub.2 through coil 59 the pressure in tank 9
can be controlled. In this regard, a pressure sensor 61 detects the
pressure of head 15 to open or close valve 63 in response to the pressure
of head 15. If the pressure of head 15, as sensed by sensor 61, rises
above a predetermined value, valve 63 is opened to allow LN.sub.2 to flow
through coil 59 and condense the head gas. When the pressure falls below
the predetermined value, valve 63 is closed. Any LN.sub.2 vaporized in
coil 59 is returned to tank 16 via line 64 thereby increasing the pressure
in tank 16.
Tank 16 is also provided with a second cooling loop 38 which carries
LN.sub.2 to and from heat exchanger reservoir 47. Reservoir 47 surrounds
cooling coil 48 located in low quantity use line 39. As LN.sub.2 is
circulated through cooling loop 38 it will sub-cool any LNG being
delivered through use line 39 to ensure that the LNG does not vaporize
during fueling. Sub-cooled LNG is LNG cooled to a temperature below its
equilibrium temperature for a given pressure and, therefore, can be used
to lower the temperature in the vehicle's fuel system.
Cooling tank 16 is provided with a vent line 19 having a pressure regulator
21 located therein. Because the heat transfer occurring at coils 48 and 59
will result in the development of nitrogen gas and a concomitant increase
in pressure in tank 16, periodically it is necessary to vent the gas in
tank 16. Regulator 21 is set such that when the pressure in the tank rises
above a predetermined value, the regulator will allow the nitrogen gas to
vent to the atmosphere. As is evident from the forgoing description, only
harmless, environmentally safe, relatively inexpensive nitrogen is vented
to the atmosphere without loss of LNG due to venting.
Two-way injection valve 45 is shown in detail in FIGS. 2 and 3. It consists
of a tubular member 70 having main control valve 71 at one and thereof
that can connect the injection valve to either line 49 or 41. The opposite
end of member 70 includes a flange 73 carrying a seal 74 and a locking
collar 75. Locking collar 75 includes screwthreads 76 that mateably engage
screwthreads 77 found on the vehicle's fuel pipe 79 such that seal 75
forms a liquid-tight fit with the end of the fuel pipe 79.
Both tubular member 70 and fuel pipe 79 include spring held check valves 80
and 82, respectively, for preventing the flow of fluid between the
vehicle's fuel tank and the fueling station of the invention. Activating
lever 79 opens both check valves such that either LNG or natural gas can
flow from tank 9 to the vehicle or natural gas can flow from the vehicle
to the fueling station as determined by the position of main control valve
71, the position of three-way valves 43 and 53, and the relative pressures
in the system. A plug 81 and cap 83 are provided to seal the injection
nozzle 45 and fuel pipe 79, respectively, when the filling operation is
completed.
In operation, LNG is delivered from storage tank 1 to pressure building
tank 9 by opening valve 12. The LNG will travel from tank 1 to tank 9 only
if the pressure in tank 9 is lower than the pressure in tank 1. Because
the pressure in tank 1 is maintained at approximately 50 psi, it is
necessary to lower the pressure in tank 9. Thus, valve 63 is opened to
allow LN.sub.2 to be conveyed through cooling line 57 and cooling coil 59
thereby to condense the gas in head 15 until the pressure in tank 9 falls
below the pressure in tank 1.
Once tank 9 is filled with LNG, its pressure can be maintained at any
desired level by using the pressure building line 23 to increase the
pressure and the cooling line 57 to decrease the pressure. Pressure
sensors 27 and 61 located in pressure building line 23 and cooling line
57, respectively, automatically open and close valves 63 and 29 to thereby
automatically maintain the pressure in tank 9 within a desired range.
When the pressurized LNG in tank 9 is to be delivered to the vehicle,
two-way injector valve 45 is connected to the fuel line 79 of the vehicle
by locking collar 75. If the pressure in the vehicle's fuel tank is too
high, line 51 can be connected to valve 45 via three-way valve 53 to
deliver the pressurized gas in the vehicle tank to tank 1. Alternatively,
line 49 can be connected to tank 9 via line 49 by valve 53 to deliver the
pressurized gas to tank 9. The orientation of valve 53 would depend on
operation preference as to whether the pressure in tank 1 or tank 9 should
be increased.
If a large quantity of LNG is desired, the delivery would be made through
line 41. In that case, three-way valve 43 would connect line 43 to valve
45. If either a small quantity a sub-cooled LNG was desired, three-way
valve 43 would connect line 39 to valve 45 and cooling loop 38 would pass
LN.sub.2 through heat exchanger 47 to sub-cool the LNG before it was
delivered through line 39.
After the vehicle's fuel tank was filled with LNG, it may be necessary to
rebuild the pressure or increase the temperature therein. In this
situation, three-way valve 53 would connect gas head 15 to injection valve
45. The high pressure gas in tank 9 would be delivered from gas head 15 to
the vehicle's fuel tank upon the opening of valve 45.
Finally, if at any time the pressure in tank 1 should rise above the
predetermined value set at regulator 33, line 31 would deliver this gas
from head 5 to tank 9 where it would be stored or condensed by coil 15.
Suitable electronic controls and sensors or gauges and manually operated
valves can be used to operate the valves in response to the demands made
on the system.
The delivery system of the invention can effectively accommodate any filly
situation that might be encountered at a vehicle fueling station. The
delivery system can control the LNG delivery temperature and pressure and
can vent or pressurize the vehicle's fuel tank through one connection. The
following are six principal vehicle tank conditions that may be
encountered at the LNG fueling station:
1) The vehicles LNG system warm and no LNG on board.
2) The vehicle LNG system nearly empty where the remaining LNG is at high
pressure/temperature conditions, near venting.
3) The vehicle LNG system nearly empty where the remaining LNG is at low
pressure/temperature conditions, near or below minimum operating
conditions.
4) The vehicle LNG system partly full where the LNG is at high
pressure/temperature conditions, near venting.
5) The vehicle LNG system is partly full where the LNG is at low
pressure/temperature conditions, near or below minimum operating
conditions.
6) The vehicle LNG system is full where the LNG is at high
pressure/temperature conditions, near venting.
While some of these conditions will be unusual, it is necessary that the
fueling station be able to accommodate all of the conditions. The fueling
station can accommodate each of these situations because it can: 1)
deliver vaporized natural gas to pressurize the vehicle tank and raise
temperature therein, 2) it can deliver LNG to lower the temperature and
pressure in the vehicle tank, or 3) it can vent natural gas from the
vehicle tank to lower the pressure and temperature therein.
While the fueling station of the invention has been described with
particular reference to LNG delivery systems, it will be appreciated that
it could also be used with other cryogens such as liquid hydrogen. Other
modifications and changes to the system will be apparent without departing
from the invention. It is to be understood that the foregoing description
and drawings are offered merely by way of example and that the invention
is to be limited only as set forth in the appended claims.
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